The answer to 'shut-off valve low water pressure' is that a shut-off valve with low water pressure is often caused by a partially closed valve or a blockage in the valve. This can happen over time as the valve mechanism wears down or mineral deposits build up. Symptoms include low water flow and pressure, especially at faucets and appliances downstream of the shut-off valve.
The solution may be as simple as fully opening the shut-off valve or clearing any debris or buildup. However, if the valve is damaged or cannot be fully opened, it will need to be replaced. This is a job that is usually best handled by a professional plumber, as they have the tools and expertise to safely and effectively replace the valve without causing further damage to the plumbing system.